The portrait depicts King Gustavus Adolphus in what traditionally has been described as a Polish costume with a red jacket decorated with braid, velvet cuffs, a lace collar and a red hat, with a view of Frankfurt-am-Main in the background. During the years 1631 and 1632, Gustavus Adolphus operated a campaign to be elected King of Poland, where his aging cousin, and arch enemy, Sigismund III still held the throne. Poland was a kingdom by election and this portrait should therefore be seen as an instrument of propaganda for the election of the throne.
According to reports from eye-witnesses the King wore this coat when he entered Frankfurt-am-Main in 1631. The view over the New Bridge in the upper right corner of the canvas should be a familiar one for Merian, as it ought to be the same as the one seen from his studio in the city. It has been argued that this portrait was actually painted by Matthaeus Merian the Younger, after the original engraving by Merian the Elder.